Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.

User Name:

Password

Please enter a password for your user account. Note that passwords are case-sensitive.

Password:

Confirm Password:

Email Address

Please enter a valid email address for yourself.

Email Address:

Insurance

Please select your insurance company (Optional)

Log-in

User Name

Remember Me?

Password

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Additional Options

Miscellaneous Options

Automatically parse links in text

Automatically embed media (requires automatic parsing of links in text to be on).

Automatically retrieve titles from external links

Topic Review (Newest First)

02-04-2012 11:51 AM

martee373

thanks guys, that seems to have taken care of the vaccum problem, now on to the next issue..i'll be driving it again before i know it lol

02-03-2012 11:22 AM

martee373

thanks for the suggestion guys, i actually did clean those ports a few months back when this throttle body was running fine on another motor but i will pull it off and check again. I didn't think to clean them again as it was running fine on another engine just a short time ago but perhaps they've become clogged up again...I will let you guys know what i find

02-02-2012 11:41 PM

DoubleVision

Ron has my thoughts exactly. You mentioned you cleaned the TBI but did you run something through each port to assure it was clean? TBI engines have a real bad habit about carbon build up. When I removed the one off my truck I found one completely caked shut with carbon and the other two were almost just as bad. If it's getting normal vacuum at the rear port then it should be on the front ports which points to there's got to be some blockage somewhere.

02-02-2012 10:21 PM

RippinRon

Ive seen the the ports right full of crud before. Pull the TB off and have a look at the bottom side of it.

02-02-2012 08:44 PM

crussell85

Get a vacuum gauge and see how much vacuum you have. What cam is in it?

02-02-2012 08:35 PM

martee373

no its not backfiring and the timing is set dead on. i checked and cleaned the egr a while back but i think i will take it off again tomorrow, something might have happened during the engine swap but it would have to be stuck open becuase there isn't enough vaccum coming off the throttle body for the computer to open it correctly

02-02-2012 08:27 PM

crussell85

Is it backfiring? If so is it out the intake or exhaust? Have you checked the egr valve?

02-02-2012 08:15 PM

martee373

yes i've sprayed all round the base of the throttle body and around the intake. and i've also checked with the hose trick, i'm not getting any engine trouble codes. It acts just like a vaccum leak though i just can't find it

02-02-2012 07:00 PM

crussell85

have you sprayed carb cleaner around the intake gaskets to check for leaks? If you find a leak it will rev the engine momentarily.

02-02-2012 05:02 PM

martee373

89 GM throttle body low vaccum on front ports of Throttle body

I have an 89 gmc sierra I just put a motor in and am expericening idling problems and acceleration problems. It acts like i'm losing vaccum somewhere but have checked several times and found no leaks. The front 3 vaccum ports of the throttle body have very little vaccum while the rear port that runs to the map sensor has normal vaccum...I have replaced the throttle body gasket and thoroughly cleaned the throttle body...does anyone have and ideas. I've been working on this truck for months and its getting very frustrating